Shipping cost for dropshipping customer

Hi all
I am building a dropshipping webshop in nopcommerce for a customer.
He has a concern regarding the business model, since he intends to have many vendors.
If he eg. charges 5EUR for shipping but the customer selects 5 cheap items from different vendors, then the 5EUR shipping wont cover actual shipping cost as each vendor would have a cost of 5EUR for shipping totally 25EUR of shipping cost.
He ask how does other get around this problem?
Also some items shipping cost may vary and exceed the 5EUR he charges, he also intends free shipping when purchase is above 40EUR, which can make matters worse if customer buys many cheap items from different vendors that will not offer free shipping for such amounts.

How does other dropshipping webshop ensure that shipping cost are covered?
He does NOT want to have higher prices to cover shipping and considers a service fee, I advised him against this as customers hate service fees.

The cost of shipping is dependant on the customer’s shopping cart. You may need to write a shipping plugin, loop through the cart and apply the vendors shippings rules to calculate the total shipping cost. Certainly can be done if the business rules are well defined.

As for free shipping over x amount, this could be tricky to implement and comment on because we don’t know the specifics. For example, you could include a rule that free shipping does not apply after a total weight is exceeded on the shopping cart. This is a simple rule but your clients case could be more complicated.

You can use additional shipping cost on product level and Free shipping over X from shipping settings.
Also you can use shipping separate option on product level at small prices product.
These out of the box option might serve you at some level.
Reference:
Product level shipping setup: https://docs.nopcommerce.com/en/running-your-store/catalog/products/add-products.html#shipping
Shipping settings: https://docs.nopcommerce.com/en/getting-started/configure-shipping/shipping-settings.html
The standard solution would be develop a new shipping provider plugin and calculate shipping cost based on vendor.
For one of our client we have developed such feature where shipping cost depends on how many vendor products you have on your cart. And each vendor has own cost. For example : Vendor1 have Cost of 5USD and Vendor2 have cost of 8USD.
Then if any customer have 1 or more items from vendor1 and 1 or more items of vendor2 then the total shipping cost will be 13USD.

If you enforce a Warehouse per vendor, and configure Shipping Settings "Use warehouse location", then the shipping provider plugin(s) will be called for each warehouse, and then finally the system will sum the separate rates into one rate the customer sees.

FYI, Shipping Director can handle complex shipping scenarios.

That looks like a solution that wont break the bank. We are running version 4.40, and it look like you support it with your solution.